Antiretroviral therapy suppresses viral load, reducing the likelihood that persons living with HIV (PLH) will transmit their infection to sexual partners. Initiation of HAART is both treatment and also a strategy to reduce future HIV incidence. Treatment-as-prevention can only be successful on a public health scale when a high proportion of PLH in the community enter, maintain, and adhere to care. A question that has received almost no scientific attention is how to reach the large number of persons in the community aware of their HIV+ status but not receiving treatment. A potentially transformative novel strategy to address this problem is by targeting interventions toward social networks of PLH in the community-particularly those not presently in care-to strengthen and reinforce network-level norms, readiness, skills, and plans for treatment entry, maintenance, and adherence. The approach is novel because it creates norms within the PLH community itself to motivate treatment engagement. This study will be conducted in St. Petersburg, Russia, where contemporary HAART regimens have only recently been rolled out but a high proportion of PLH are not in care, decline prescribed HAART therapy, or interrupt treatment. UNAIDS data show that the proportion of PLH in Eastern Europe outside of medical care is higher than in Subsaharan Africa, and two-thirds of PLH receiving HAART do not adhere at optimal levels. Our pilot research has established that PLH have many other PLH in their social networks, and that these networks can be identified and engaged in behavioral intervention. A 6- month period of formative study will be undertaken to tailor recruitment and intervention methods. The study's main trial will recruit 32 3-ring sociocentric social networks of PLH (n=448). Baseline assessments will be made of each participant's CD4+ and HIV viral load, care engagement, HAART adherence, and psychosocial characteristics. Networks will be randomized in equal numbers to two study conditions. Comparison condition network members will receive a care motivational interview at baseline and then usual services. Members of each of the 16 social networks assigned to the intervention condition will receive the same motivational interview session to prime interest in care. Then, socially influential network leaders, identified based o sociometric standing and centrality in the network's structure, will be trained to deliver ongoing theory-based, personally-tailored advice and counseling to other PLH network members over a 2-month period. Leaders will emphasize the benefits of entering, remaining, and adhering to treatment. The network intervention's aim is to boost the proportion of network members engaged in medical care, increase care attendance, reduce viral load, and improve treatment adherence at 6- and 12-month followup. We will examine how network structural characteristics mediate intervention effects, and will also model intervention impact for reducing subsequent incidence. The study's impact rests on the potential for network interventions to engage PLH in the community to enter and adhere to care. The modality will be applicable to international settings and in the United States.